IES20130133A2 - Mains electricity frequency measurement system for control of electrical power devices - Google Patents

Abstract

The invention relates to the measurement of electricity frequency, and frequency changes, with a high level of precision at low cost, thus enabling a range of domestic energy awareness devices not commercially feasible before this invention. Energy awareness device can now use mains electric frequency to optimize power usage and relieve stress on the grid. <Figure 1>

Description

Mains Electricity frequency measurement system for control of electrical power devices Intro duction Field of the invention The invention relates to the measurement of electricity frequency, and frequency changes, with a high level of precision at low cost, thus enabling a. range of domestic energy awareness devices not commercially feasible before this invention. Energy awareness device can now use Mains electric frequency to optimize power usage and relieve stress on the grid.

Prior Art Discussion It is recognised that the measurement of elec(ricity frequency has been done for a. number of years. This has been particularly important in hardware engineering where the quality of power supply is a key issue. Equipment used is specialized aud relatively expensive. In the domestic sector the method used is an inventive step which allows the cost of detailed frequency analysis to be cut considerably. This facilitates the commercial viability of a range of frequency measurement and display devices for home use, A number of embodiments of these devices are discussed below. 1 3 3 Advantages Allows very sensitive electricity frequency analysis.

Allows low cost frequency analysis thus making commercially possible a range of domestic devices. f· Allows high electrical power devices to automatically adapt ίο network problems Allows network operators to have automatic spinning reserve devices in domestic use Sttmmai-y of the Invention Accoiding to the invention, there is provided here a method of measuring electricity frequency to a high precision at low cost, thus enabling a range of domestic display devices which will help to promote energy awareness. The method comprises the steps:The conversion of electrical frequency from analogue (capture) to digital with high precision High rate of digi Lal sampling of the frequency 10,000 /see) to allow very accurate measurement An algorithm to analyse these frequency samples and detect minute changes to its value A method to display the frequency and frequency changes in an intuitive way to the end user A device to be installed in domestic and industrial settings which allows tire power device to adapt to network demands IE 1 J Ο 1 3 3 Detailed Description of Invention Figure 1 shows the schematic layout of the Frequency Monitoring Device. Fig 1(1) has the main electrical power supply coixneciing into the device. Mains over voltage protection is provided by the varistor Fig 1(1) The transformerless power supply created by Fig 1 (I) give out a 5 volt supply which is used to power the circuit. Fig 1(2) is an opto-isolater circuit which is used to sample the mains electrical voltage and prevent any high voltage from passing into the rest of the circuitry. This sample signal is processed into a usable signal by a two stage transistor amplifier Fig 1(3) for the micro-controller Figi (4) to sample and convert this signal into a frequency based number reflecting the current frequeny of the mains supply. Fig 1(5) is a two part control circuit which allows the micro-controller Figi (4) to control the latching relay circuit Fig 1(5) using two simple transistor switches Fig 1(6). 'ihe low power transformerless supply Figl(l) eliminates the need for a transformer and reduces dimensions and cost of the device. The micro-controller fig 1(4) uses a program to convert the voltage sample signal into a frequency which is monitored. The frequency sensed is indicative of the state of the mains electrical network as frequencies under 49 hertz reflect loading or stress on the power grid. By monitoring this fiOquency the device can connect the relay Fig 1(5) and provide power to the end load, a healer or water system. The constant measurement of frequency means that network changes and problems are register and acted upon almost instantaneously.

Figure 2 shows the layout of the device. Power is supplied Fig 2(1,2) into the device via connectors fig 2(3) The latching relay Fig 2( 12) interrupts the main electrical 3 0 1 33 supply to the end load via connectors Fig 2(4) and cabling Fig 2(5,6) The transformer-less power supply is assembled at Fig 2(7) and provides 5 voh$ to power the unit. Micro-controller Fig 2(8) senses the frequency into the unit aud controls the latching relay Fig 2(12) via two transistors switches Fig2 (10,11) As there is a small current available form the device power supply Fig 2(7) which is * stored in a super capacitor Fig 2(9) to allow lor tire higher switching current required by tire latching relay Fig 2(12) Fig 3 shows liow the device will be installed in a domestic situation. Mains power cabling tig 3(4) is connected of the Frequency Monitor Device Fig 3(2). In turn power from the device Fig 3(2) is connected to a standard circuit breaker Fig 3(3) which protects the electrical system Fig 3(7) from overload and earthing problems. The power to the heating systems is via cabling system Fig 3(6) Fig 4 explains the power control algorithm used. When power Fig 4(x) is applied to tlie system with no frequency perturbation, power is transferred out io tlie end load Fig 4(1) Upon main frequency drops power will be stopped Io the load Fig 4(2) The algorithm controls the time taken to restart the power flow which can be program med to allow the overall network to recover from any issues. When power is restored Fig 4(3) a random number generator controls the turn on time for a particular device Fig 4(4) Using a random number from 0-1000 means at any one second period statistically only 0.1% of all loads controlled by such devices will turn on again. This in effect creates ail asymmetric hysteresis allowing for instantaneous powering off of large electrical loads oil a network but a slow return of power after network stabilization.

Claims (4)

1. In one embodiment, the device will use a frequency convener to sense ihe actual

2. 5 mains electrical frequency to allow power control of electrical devices On another embodiment, the device can sense electrical network power frequencies X and deviations On another embodiment, the device can have a graduated response to network frequency changes

3. 10 On another embodiment, the device allows noise signals in electrical power supplies to be filters out Oil another embodiment, the device allows for drifting signals sensing to be filter out On another embodiment, the device filters high frequency signa] spikes

4. 15 On another embodiment, the device uses a proportional, intergrated, differentiated control mechanism to control power On another embodiment, the device uses a semi state control output for low power control On another embodiment, the device uses a power relay system for medium power 20 systems On another embodiment, the device can use a power contactor for high power control systems On another embodiment, the device is tunable by an external microcontroller On another embodiment, the device can be tuned to 60Hz electrical systems 25 On another embodiment, the device can be used to shutdown remotely a power /£ί 30 1 3 3 device On another embodiment, the device can be tunable to different electrical loads including inductive and capacitive 5 On another embodiment, the device can be integrated into household appliances such as fridges, cookers and shower uuiLs On another embodiment, the device has built in hysteresis to cater for resonance and self oscillation